This video has two kneeling postures for flexibility in the hips/pelvis. The second posture (crescent lunge) also opens the front of the body, creating a back extension - good for if you sit a lot.

A folded blanket or towel under the knees is nice for cushioning. If you are not comfy kneeling, don't bother with these. You can do a standing version of tiger by lifting the knee in front and then legthening it back behind you, instead, and a standing lunge position.